#include<bits/stdc++.h>
#define INF 0x3f3f3f3f
#define mod 998244353
#define endl '\n'
using namespace std;
typedef long long LL;
typedef pair<int, int>PII;
const int N = 6000;
int n;
int f[N];
struct Node {
  int a, b;
}node[N];
bool cmp1(Node a, Node b) {
  return a.a < b.a;
}
bool cmp2(Node a, Node b) {
  return a.b < b.b;
}
void solve() {
  cin >> n;
  for (int i = 1; i <= n; ++i) {
    scanf("%d%d", &node[i].a, &node[i].b);
  }
  sort(node + 1, node + 1 + n, cmp1);
  for (int i = 1; i <= n; ++i) {
    f[i] = 1;
    for (int j = 1; j <= i; ++j)
      if (node[j].b < node[i].b)
        f[i] = max(f[i], f[j] + 1);
  }
  int res = -INF;
  for (int i = 1; i <= n; ++i) {
    res = max(res, f[i]);
  }
  sort(node + 1, node + 1 + n, cmp2);
  for (int i = 1; i <= n; ++i) {
    f[i] = 1;
    for (int j = 1; j <= i; ++j)
      if (node[j].a < node[i].a)
        f[i] = max(f[i], f[j] + 1);
  }
  for (int i = 1; i <= n; ++i) {
    res = max(res, f[i]);
  }
  cout << res << endl;
}
int main() {
  //int t; cin >> t;
  //while (t--)
    solve();
  return 0;
}